游离态氨基酸对羊角月牙藻的生物有效性

Bioavailability of dissolved free amino acids to alga Selenastrum capricornutum

采用实验室模拟培养试验,以6种个体氨基酸——丝氨酸、天冬氨酸、谷氨酸、甘氨酸、丙氨酸和精氨酸为唯一氮源,采用一次性培养的方法,在无菌条件下,研究羊角月牙藻对不同种类个体氨基酸和不同浓度混合氨基酸的利用潜能。结果表明:藻细胞在生长过程中会释放氨基酸增加水体中氨基酸浓度,同时,藻类可迅速并直接利用多种游离态氨基酸快速生长。氨基酸浓度在培养周期的前2天减少90%以上,藻细胞数在第6~8天达到最大,说明藻细胞的生长滞后于游离氨基酸浓度的下降;在个体氨基酸试验中,藻细胞对氨基酸的利用程度为精氨酸>丙氨酸>谷氨酸>天门冬氨酸>丝氨酸>甘氨酸;在混合氨基酸试验中,藻细胞的比增殖速率明显高于个体氨基酸试验组,且随混合氨基酸浓度的增加,最大藻细胞生物量增加;羊角月牙藻在利用个体氨基酸的同时也会释放其他种类的氨基酸,其中,天冬氨酸和甘氨酸的释放浓度最大。羊角月牙藻在无机氮缺乏情况下,能迅速利用氨基酸。

order to understand the incubation process of algae on the low concentrations of dissolved free amino acids （DFAA） , the growth of Selenastrum capricornutum was studied in the laboratory. Six individual amino acids, i.e. serine, aspartic acid, glutamic acid, glycine, alanine and arginine, were used as the sole and mixed nitrogen sources for algal incubation under axenic conditions. The results showed that algae were able to utilize various amino acids for growth; meanwhile, algae could spread different amino acids in the incubation. DFAA concentration decreased with up to 90% in the 2 days, while the cells number of algae reached to the maximum in the 6-8 days, meaning that the growth of algae cell number lags behind the decrease of the of DFAA content. In the individual amino acids experiments, rank order of the use of amino acid was： arginine 〉 alanine 〉 glutamie acid 〉 aspartic acid 〉 serine 〉 glycine. In the mixed amino acids experiments, the cell proliferation rate of algae was significantly higher than that of individual amino acid group; meanwhile with the increase of mixed amino acid concentration, the maximum number of algal cells was also increased. Selenastrum capricornutum can also release other kinds of amino acids in the use of the individual amino acid, among them, the main release amino acids are aspartic acid and glyeine. Algae could use amino acid rapidly in the lack of inorganic nitrogen condition, which provided a theoretical basis to illustrate dissolved organic nitrogen promotes algae growth.